Carbonaceous material, its production process and electric double layer capacitor employing it

Abstract

A carbonaceous material having a total pore volume of from 0.5 to 1.5 cm 3 /g per unit mass, a volume of micropores having diameters of from 10 to 20 Å of from 10 to 45% based on the total pore volume, a volume of mesopores having diameters of from 20 to 200 Å of from 35 to 65% based on the total pore volume, a volume of macropores having diameters exceeding 200 Å of not more than 15% based on the total pore volume, and a specific surface area of from 1,000 to 2,500 m 2 /g. The carbonaceous material is incorporated into an electric double layer capacitor to provide increased capacitance.

1. A carbonaceous material which has a total pore volume of from 0.5 to 1.5 cm 3 /g per unit mass, a volume of micropores having diameters of from 10 to 20 Å of from 10 to 45% based on the total pore volume, a volume of mesopores having diameters of from 20 to 200 Å of from 35 to 65% based on the total pore volume, a volume of macropores having diameters exceeding 200 Å of not more than 15% based on the total pore volume, and a specific surface area of from 1,000 to 2,500 m 2 /g. 
     
     
       2. The carbonaceous material of  claim 1 , wherein the volume of micropores having diameters of from 10 to 20 Å is from 10 to 25% based on the total pore volume. 
     
     
       3. The carbonaceous material of  claim 1 , wherein the volume of mesopores having diameters of from 20 to 200 Å is from 40 to 60% based on the total pore volume. 
     
     
       4. The carbonaceous material of  claim 1 , wherein the volume of macropores having diameters exceeding 200 Å is not more than 10% based on the total pore volume. 
     
     
       5. The carbonaceous material of  claim 1 , wherein the specific surface area is from 1,000 to 2,200 m 2 /g. 
     
     
       6. The carbonaceous material of  claim 5 , wherein the specific surface area is from 1,000 to 1,500 m 2 /g. 
     
     
       7. The carbonaceous material of  claim 1 , having a total pore volume of from 0.85 to 1.44 cm 3 /g. 
     
     
       8. The carbonaceous material of  claim 5 , having a specific surface area of from 1,500 to 2,100 m 2 /g. 
     
     
       9. An electric double layer capacitor having electrodes comprising a carbonaceous material having a total pore volume of from 0.5 to 1.5 cm 3 /g per unit mass; a volume of micropores having diameters of from 10 to 20 Å of from 10 to 45% based on the total pore volume, a volume of mesopores having diameters of from 20 to 200 Å of from 35 to 65% based on the total pore volume; a volume of macropores having diameters exceeding 200 Å of not more than 15% based on the total pore volume, and a specific surface area of from 1,000 to 2,500 m 2 /g. 
     
     
       10. The electric double layer capacitor of  claim 9 , which has an organic electrolytic solution. 
     
     
       11. The electric double layer capacitor of  claim 10 , wherein the organic electrolytic solution contains at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetonitrile, glutaronitrile, valeronitrile, sulfolane and a 3-methylsulfolane, and a salt comprising a quaternary onium cation represented by R 1 R 2 R 3 R 4 N +  or R 1 R 2 R 3 R 4 P + , wherein each of R 1 , R 2 , R 3  and R 4 , which is independent of one another, is a C 1-6  alkyl group, and at least one anion selected from the group consisting of BF 4   − , PF 6   − , CO 4   − , CF 3 SO 3    −  and (SO 2 R 5 ) (SO 2 R 6 )N − , wherein each of R 5  and R 6 , which is each independent of one another, is a C 1-4  alkyl group. 
     
     
       12. A process for producing an electric double layer capacitor having electrodes comprising a porous carbonaceous material and a binder, wherein the carbonaceous material is obtained by the steps of:
 (1) curing a liquid thermosetting resin which contains a volatile component having a boiling point of from 120 to 400° C. and which has a viscosity of from 0.1 to 100 Pa·s at 25° C., to obtain a cured product;  
 (2) pulverizing the cured product;  
 (3) carbonizing the pulverized, cured product in a non-oxidizing atmosphere so that the mass reduction till 400° C. in the carbonization is from 2 to 50 mass % of the mass before carbonization, to obtain a carbonized product; and  
 (4) activating the carbonized product.  
 
     
     
       13. The process of  claim 12 , wherein, in the step (1), a curing agent is added to the thermosetting resin, followed by kneading, and further, a curing accelerator is added thereto, followed by kneading to obtain a kneaded product, and then said kneaded product is cured to obtain a cured product. 
     
     
       14. The process of  claim 13 , wherein the curing agent is added in an amount of at least 1 mass % based on the thermosetting resin. 
     
     
       15. The process of  claim 12 , wherein the curing accelerator is added in an amount of at most 5 mass % based on the thermosetting resin. 
     
     
       16. The process of  claim 12 , wherein the thermosetting resin is a phenolic resin. 
     
     
       17. The process of  claim 12 , wherein after the step (4) has been completed, the carbonaceous material has a total pore volume of from 0.5 to 1.5 cm 3 /g per unit mass, a volume of micropores having diameters of from 10 to 20 Å of from 10 to 45% based on the total pore volume, a volume of mesopores having diameters of from 20 to 200 Å of from 35 to 65% based on the total pore volume, a volume of macropores having diameters exceeding 200 Å of not more than 15% based on the total pore volume, and a specific surface area of from 1,000 to 2,500 m 2 /g. 
     
     
       18. A process for producing a porous carbonaceous material, which comprises the steps of:
 (1) curing a liquid thermosetting resin which contains a volatile component having a boiling point ranging from 150° to 380° C. and which has a viscosity ranging from 0.2 to 80 Pa·s at 25° C. to obtain a cured product;  
 (2) adding at least 1 mass % of a curing agent, based on the thermosetting resin;  
 (3) pulverizing the cured product;  
 (4) carbonizing the pulverized cured product in a non-oxidizing atmosphere so that the mass reduction which occurs upon heating up to a temperature of 400° C. during carbonization ranges from 2 to 50 mass % of the mass before carbonization, thereby obtaining a carbonized product; and  
 (5) activating the carbonized product.  
 
     
     
       19. The process of  claim 18 , wherein after the addition of the curing agent to the thermosetting resin in step (2), kneading is effected and then a curing accelerator is added thereto, and then further kneading is effected, and then the kneaded product is cured to obtain a cured product. 
     
     
       20. The process of  claim 19 , wherein the curing accelerator is added in an amount of at most 5 mass % based on the thermosetting resin. 
     
     
       21. The process of  claim 18 , wherein the thermosetting resin is a phenolic resin. 
     
     
       22. The process of  claim 18  wherein after the carbonized product has been activated in step (5), the carbonaceous material has a total pore volume ranging from 0.5 to 1.5 cm 3 /g per unit mass, a volume of micropores having diameters ranging from 10 to 20 Å of from 10 to 45% based on the total pore volume, a volume of mesopores having diameters of from 20 to 200 Å ranging from 35 to 65% based on the total pore volume, a volume of macropores having diameters exceeding 200 Å of not more than 15% based on the total pore volume, and a specific surface area of from 1,000 to 2,500 m 2 /g. 
     
     
       23. The process of  claim 18 , wherein the boiling point of the liquid thermosetting resin ranges from 180 to 350° C. and the viscosity of the liquid ranges from 0.5 to 50 Pa·s.